1. Field of the Invention
The invention relates to a novel locking mechanism for locking the piston rod of a fluid responsive valve actuator in at least one of first and second positions respectively corresponding to the open and closed positions of a valve member manipulated by the actuator.
2. Description of the Prior Art
In oil fields, pipe lines, and refineries there has been a considerable need for a fluid actuated valve actuator which, in the event of an emergency causing the reduction or loss of control pressure supplied to the actuator, would be mechanically locked in the position it held prior to the occurrence of the emergency. Depending upon the particular application, it may be desirable that the fluid operated valve actuator be mechanically locked in either its open or its closed position. More importantly, there are a significant number of valves requiring cycling operations between an open and closed position and it is desirable that such valves be locked in the same position as existed prior to the occurrence of the particular emergency. In a more common parlance, it is therefore desirable that a valve actuator be capable of being locked in an up position, a down position, or either an up or down position in the event of loss of, or reduction in, control pressure supplied to such valve actuator.